Biology subjects

Flores, H. A.

Publications and source records attributed to Flores, H. A..

5 recordsLinked to original sources

bioRxiv2025

High genomic stability of wMel Wolbachia after introgression into three geographically distinct Aedes aegypti populations

The introgression of wMel Wolbachia into Aedes aegypti populations is being used for the biocontrol of arboviruses such as dengue and chikungunya in 15 countries to date. A wMel infection in Ae. aegypti both reduces the transmission of viruses by the mosquito and causes a reproductive manipulation that aids wMel introgression into naive populations. However, a critical concern is whether wMel could evolve over time, potentially diminishing these desired phenotypes. Here, we investigated the stability of the wMel genome in Ae. aegypti released for biocontrol in Colombia, Indonesia, and Vietnam. We sequenced the wMel genome at the start of releases and up to six years after wMel introgression into each population. Our study identifies very few genomic changes, suggesting the wMel genome is not rapidly evolving despite its release into three geographically different field sites and subsequent exposure to novel environments. These results align with previous wMel sequencing studies from Australia and provide strong evidence for the long-term genomic stability of wMel, reinforcing its potential as a reliable biocontrol tool against Ae. aegypti-transmitted arboviruses.

evolutionary biology↗

bioRxiv2025

Targeted knockdown of in vitro candidates does not alter Wolbachia density in vivo

The bacterial endosymbiont Wolbachia has emerged as an effective biocontrol method to reduce arbovirus transmission. Transinfection of wMel Wolbachia from Drosophila melanogaster to Aedes aegypti results in the transfer of important Wolbachia-induced phenotypes including the reproductive modification, cytoplasmic incompatibility, and inhibition of viruses including dengue and chikungunya. However, the mechanisms underlying these critical traits as well other Wolbachia-host interactions are still not fully understood. Recently an in vitro genome wide RNAi screen was performed on wMel-infected Drosophila S2 cells and identified large cohorts of host genes that alter wMel density when targeted. If these findings can be replicated in vivo, this would provide a powerful tool for modulating wMel density both systemically and in a tissue-specific manner allowing for interrogation of wMel-host interactions. Here, we used the GAL4/UAS system to express RNAi molecules targeting host gene candidates previously identified to dysregulate wMel density in vitro. We found systemic knockdown of two candidate D. melanogaster genes does not lead to wMel density dysregulation. To explore the lack of consistency between our study and previous work, we also examined native tissue-specific density of wMel in D. melanogaster. We show density is varied between tissues and find that individual tissue densities are not reliable linear predictors of other tissue densities. Our results demonstrate the complexities of implementing in vitro findings in systemic applications.

genetics↗

bioRxiv2024

Wolbachia introgression in Ae. aegypti is accompanied by variable loss - a multi-country assessment

The wMel and wAlbB strains of the bacterial endosymbiont Wolbachia are being introgressed into Aedes aegypti populations as a biocontrol method to reduce the transmission of medically important arboviruses. Successful introgression of Wolbachia relies on both persistence of Wolbachia throughout the host life cycle and a high fidelity of maternal transmission of Wolbachia between generations. wMel has been introgressed into field populations in 14 countries to date. Monitoring of field sites has shown that wMel prevalence can fluctuate substantially over time, prompting concerns this could lead to reduced efficacy of the biocontrol method. To explore the fidelity of wMel persistence and transmission, we developed molecular methods to measure the prevalence of Ae. aegypti negative for Wolbachia infection but carrying the "founder" mitochondrial haplotype of the single female first transinfected. As all released wMel-infected mosquitoes and any subsequent offspring will carry this founder mitochondrial haplotype, any mosquitoes with this mitochondrial haplotype and without wMel indicate that wMel was lost from this lineage at some point. We observed loss of wMel ranging from 0 to 20.4% measured at various time intervals after wMel-infected mosquito releases in five different countries. Despite some field sites showing Wolbachia loss, overall Wolbachia prevalence was sustained during the time periods studied. We then employed laboratory studies to explore factors that could contribute to the loss of wMel. Surprisingly, near-perfect maternal transmission was measured across laboratory conditions of early blood feeding, starvation, and salinity. Collectively, these findings underscore that although wMel transmission can be imperfect it does not necessarily undermine population-level establishment, providing encouragement that the intervention will be robust in most dengue-endemic environments.

ecology↗

bioRxiv2023

Antiviral Wolbachia strains associate with Aedes aegypti endoplasmic reticulum membranes and disturb host cell lipid distribution to restrict dengue virus replication.

The insect endosymbiotic bacterium Wolbachia pipientis is being utilised as a biocontrol tool to reduce the incidence of Aedes aegypti-transmitted viral diseases like dengue. However, the precise mechanisms underpinning Wolbachias antiviral activity are not well defined. Here we generated a panel of Ae. aegypti-derived cell lines infected with antiviral strains wMel and wAlbB or the non-antiviral strain wPip to understand host cell morphological changes specifically induced by antiviral strains. Antiviral strains were frequently found to be entirely wrapped by the host endoplasmic reticulum (ER) membrane, while wPip bacteria clustered separately in the host cell cytoplasm. ER-derived lipid droplets (LDs) increased in volume in wMel-and wAlbB-infected cell lines and mosquito tissues compared to cells infected with wPip or Wolbachia-free controls. Inhibition of fatty acid synthase (required for triacylglycerol biosynthesis) reduced LD formation and significantly restored ER-associated dengue virus replication in cells occupied by wMel. Together, this suggests that antiviral Wolbachia strains may specifically alter the lipid composition of the ER to preclude the establishment of DENV replication complexes. Defining Wolbachias antiviral mechanisms will support the application and longevity of this effective biocontrol tool that is already being used at scale. ImportanceAedes aegypti transmits a range of important human pathogenic viruses like dengue. However, infection of Ae. aegypti with the insect endosymbiotic bacterium, Wolbachia, reduces the risk of mosquito to human viral transmission. Wolbachia is being utilized at field sites across more than 13 countries to reduce the incidence of viruses like dengue, but it is not well understood how Wolbachia induces its antiviral effects. To examine this at the subcellular level, we compared how different strains of Wolbachia with varying antiviral strengths, associate with and modify host cell structures. Strongly antiviral strains were found to specifically associate with the host endoplasmic reticulum and induce striking impacts on host cell lipid distribution. Inhibiting Wolbachia-induced lipid redistribution partially restored dengue virus replication demonstrating this is a contributing role for Wolbachias antiviral activity. These findings provide new insights into how antiviral Wolbachia strains associate with and modify Ae. aegypti host cells.

microbiology↗

bioRxiv2020

Novel phenotype of Wolbachia strain wPip in Aedes aegypti challenges assumptions on mechanisms of Wolbachia-mediated dengue virusinhibition .

The bacterial endosymbiont Wolbachia is a biocontrol tool that inhibits the ability of the Aedes aegypti mosquito to transmit positive-sense RNA viruses such as dengue and Zika. Growing evidence indicates that when Wolbachia strains wMel or wAlbB are introduced into local mosquito populations, human dengue incidence is reduced. Despite the success of this novel intervention, we still do not fully understand how Wolbachia protects mosquitoes from viral infection. Here, we demonstrate that the Wolbachia strain wPip does not inhibit virus infection in Ae. aegypti. We have leveraged this novel finding, and a panel of Ae. aegypti lines carrying virus-inhibitory (wMel and wAlbB) and non-inhibitory (wPip) strains in a common genetic background, to rigorously test a number of hypotheses about the mechanism of Wolbachia-mediated virus inhibition. We demonstrate that, contrary to previous suggestions, there is no association between a strains ability to inhibit dengue infection in the mosquito and either its typical density in the midgut or salivary glands, or the degree to which it elevates innate immune response pathways in the mosquito. These findings, and the experimental platform provided by this panel of genetically comparable mosquito lines, clear the way for future investigations to define how Wolbachia prevents Ae. aegypti from transmitting viruses. Author summaryDengue virus, transmitted by the Aedes aegypti mosquito, is one of the fastest-growing infectious diseases, causing an estimated 390 million human infections per year worldwide. Vaccines have limited efficacy and there are no approved therapeutics. This has driven the rise of novel vector control programs, in particular those that use the bacterium, Wolbachia, which prevents transmission of dengue and other human pathogenic viruses when stably introduced into Ae. aegypti populations. Although this is proving to be a highly effective method, the details of how this biocontrol tool works are not well understood. Here we characterise a new Wolbachia strain, wPip, and find that Ae. aegypti carrying wPip are still able to transmit dengue similar to mosquitoes that do not carry Wolbachia. This finding has allowed us to begin a rigorous program of comparative studies to determine which features of a Wolbachia strain determine whether it is antiviral. Understanding these mechanisms will enable us to predict the risk of viral resistance arising against Wolbachia and facilitate preparation of second-generation field release lines.

microbiology↗